One important requirement for an identification document is that it needs to provide adequate measures for preventing counterfeiting, tampering, or forging of the identification document. An identification document can be an ID card, a membership card, or a credit or bank card, etc. The face image of the holder is often included on the identification document, which has been a rather effective feature for preventing the unauthorized use of the identification document.
However, as digital imaging technologies become increasingly advanced and widely available, counterfeiting is also becoming more sophisticated and more difficult to prevent. One example of the digitally assisted counterfeiting is that after the theft of an identification document, a counterfeiter can digitally scan the image on a identification document with a high-resolution digital scanner (such as a 1200 dpi flat bed scanner that is widely available). The scanned-in digital image is then processed on a computer using a commercial image processing software such as Adobe Photoshop or Corel's CorelDraw for sharpening, artifact removal, color and tone management. With the image processing software, the counterfeiter can easily replace the face of the intended holder by a different person while almost seamlessly matching the background of the face, to produce a fraudulent image. This fraudulent image is then printed on a blank substrate such as a plastic card to produce a counterfeit identification document. The digital imaging technologies have currently advanced to such a stage that this fraud identification document can appear almost identical to the original document to the naked eyes.